DESCRIPTION: The primary hypothesis under investigation is that humoral and cellular immune responses will affect the biological properties and genetic characteristics of HIV and alter disease progression. The proposed studies will utilize available specimens from a cohort followed longitudinally since 6 months of age or earlier, and focusing primarily on slow progressors and rapid progressors. The Specific Aims of this application are: (1) to study the natural history of humoral immune responses through quantitation of binding antibodies to core and envelope, quantitation of autologous and heterologous neutralizing antibody, and detection of ADCC; (2) to determine the role of cellular immunity in disease progression through characterization of T cell receptor utilization and CTL; (3) to study the biological properties of virus over time as it relates to disease progression by determining viral burden, host cell range and syncytia production.